Energy loss spectra are suitable for detecting elementary excitations of a sample, such as excitation of surface plasmons in the sample, for example. To this end, for example a monochromatic electron beam can be directed onto the sample, resulting in excitations of the sample and a reduction of the kinetic energy of electrons of the beam by an amount corresponding to the energy of the excitation. If an energy spectrum of the electron beam subsequent to its interaction with the sample is recorded, the recorded energy spectrum contains information relating to the excitation energies. The articles J. Nelayah, L. Gu, W. Sigle, C. T. Koch, I. Pastoriza-Santos, L. M. Liz-Marzán, and P. A. van Aken, “Direct imaging of surface plasmon resonances on single triangular silver nanoprisms at optical wavelength using low-loss EFTEM imaging”, Opt. Lett. 34, 1003-1005 (2009) and Wilfried Sigle, Jaysen Nelayah, Christoph T. Koch, and Peter A. van Aken, “Electron energy losses in Ag nanoholes—from localized surface plasmon resonances to rings of fire,” Opt. Lett. 34, 2150-2152 (2009) describe applications of this method.